During the winter months in many northern climates the surface of a lake will freeze over with a depth of ice sometimes exceeding 24 inches. Avid anglers continue to fish during these winter months by cutting holes through the ice and catching fish through these holes. The air surface temperature is typically below 32 degrees Fahrenheit which has a tendency to continually refreeze the water in the fishing holes unless proactive steps are taken to keep the water in the hole from freezing. At times, it may become necessary for the angler to regularly skim the forming ice off the water surface to avoid a line frozen in the ice. Ice forming in the holes is undesirable and distracts the angler from focusing on catching fish.
Various devices have been contrived in an attempt to prevent the fishing holes from freezing over. For example, heat sources have been described to heat the water in the ice fishing hole sufficiently so that the adjacent air is not able to freeze the water. These devices require significant sources of energy (either electric or from combustible materials) to transfer heat, warm the water, and maintain the air or water temperature above freezing over an extended period of time. These devices also tend to block the fishing hole and interfere with the angler's ability to fish through the hole unobstructed. Also, in order to avoid a likely entanglement, many of these devices are required to be removed from the hole before an attempt is made to pull a fish up through the hole.
Other attempts have been made to provide a way to conveniently fish through the ice during the winter months. By way of example, movable fishing shacks or houses have been constructed with one or more holes formed in the floor of the shack. The shack is positioned on the lake where the angler wants to fish and then the shack is typically lowered so that the floor of the shack is close to the ice surface. An auger is used to drill holes in the ice that are aligned with the holes in the floor. It is common for fishing shacks to have some form of propane or electric heater to increase the air temperature within the shack. However, the walls of the fishing shack are typically thin to reduce weight and are not well insulated. Hence, the fishing holes near the heater tend to stay open while the fishing holes at the opposite end of the shack tend to be more likely to freeze over.
Also, although the floor is close to the surface of the ice, outdoor air may circulate under the shack and the air temperature adjacent the hole may drop below the freezing temperature of water. Even in heated fishing shacks if the hole is left unattended a layer of ice may form over the hole and may freeze the fishing line into the ice. At night time, while the anglers sleep, it is especially common for a layer of ice to form in the hole. Open air fishing in conjunction with fishing from a house is also common, however, the holes tend to freeze over even faster without proactive management. It is desirable to reduce the likelihood that ice will form in a fishing hole so that the angler is able to focus on fishing rather than fishing hole maintenance. It is further desirable to maintain the fishing hole free of ice without interfering with the ability to fish in the hole and without requiring removal of a device from the hole prior to pulling a fish through the hole.